Water Wisteria (hygrophila Difformis) Toxicity?

Plant tormentor

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Jan 5, 2021
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Hi.
I've posted this question to several farcebook aquatic plant groups but so far gotten no replies. I'm hoping there may be some wiser minds here who can help. As a new member i can't post links yet but will endevor to do so when i can. For now i'll otherwise include the name of the paper and authors of items mentioned.

Has anyone experienced or otherwise come across any information relating to toxicity issues with water wisteria (Hygrophila difformis)? I heard a vauge, non-descript and unreferenced mention of H. difformis toxicity and wanted to find out more details. Tracking back references, the origin of the claim seems to primary come from one paper (A Details study on Hygrophila difformis by Samanta Krishanu) which states:

"When first submerged in an aquarium or pond this glands produce a toxic substances that may be toxic to some fish. So take great care when handling than as any damage seems to give off the toxin. Once they have been in the water a while the poison seems to disappear."

The paper provides no further illumination into the matter. It seems there have been a few studies into H. difformis and it's extracts however, at least some of which may provide some possible clues, though i'm struggling with terminology. One study looked at anesthetic properties in mice and found it effective (and non-toxic). Another looked at it as a control mechanism for flat worms, and another, possibly the most promising, looked at it as an inhibitor for some cyanobacteria "due possibly to its release of toxic phosphorus-containing allelochemicals". I haven't been able to find the full text of the latter paper but the abstract is available under the paper's name,
Inhibitory effects of Hygrophila difformis on the growth of Microcystis aeruginosa by Meng Lihua, Liu Yixin.

I don't really understand what is meant by 'toxic phosphorus-containing allelochemicals' however i gather it is something akin to herbicidal properties? Not really sure. If anyone is able to translate botanist to English or is otherwise familiar with any concrete information relating to toxicity, i'd be interested to hear.

Cheers.
 

tiger15

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Are you sure it is not referring to Hornwort CERATOPHYLLUM DEMERSUM, a look alike aquatic plant that is known to release allelochemical that can inhibit algae growth. It is used in ponds to suppress algae. Hygrophila difformis is a tropical plant that cannot survive in temperate zone and is not known to be toxic to fish, plants or algae in aquarium.
 
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Plant tormentor

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Jan 5, 2021
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Thanks for your reply tiger. The only name i have is 'water wisteria' which i am taking to mean Hygrophila difformis. I am in Australia and both Hygrophila difformis and Ceratophyllum demersum are common here as both wild and cultivated plants. It seems unlikely they'd be confused, particularly given emersed growing H. difformis has very different, oval shaped leaves when growing emersed. Side by side, emersed and submerged growth look like totally different plants. I did come across a study that seemed to indicate certain extracts may be in aerial growing leaves, presumably in contrast to submerged growth. It is more the emersed to submerged phase i'm interested in as that seems to be where the question really lays.

Are you sure it is not referring to Hornwort CERATOPHYLLUM DEMERSUM, a look alike aquatic plant that is known to release allelochemical that can inhibit algae growth. It is used in ponds to suppress algae. Hygrophila difformis is a tropical plant that cannot survive in temperate zone and is not known to be toxic to fish, plants or algae in aquarium.
 

Plant tormentor

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Jan 5, 2021
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Just for anyone curious, these are both Hygrophila difformis. The stem on the left is from an emersed growing plant whereas the stem on the right is from a (slightly nutrient deficent) submerged growing plant.

Also, for anyone who wants to look the first paper over it's available here:

A Details study on Hygrophila difformis by Samanta Krishanu -
http://www.ijpcbs.com/files/volume2-4-2012/12.pdf

water wisteria leaf differences 140121.jpg
 

Chris Noto

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I've never heard anything about Hygrophila toxicity.

I'd caution you on interpreting the information in the pharmacy research paper to mean anything at all in terms of the plant's effect in an aquarium setting. The author, a pharmacy grad student, post-doc, or already degreed researcher, is looking for a way to publish something, anything, as part of their required professional activity. The paper must provide some kind of new information. The author seems to be looking for some kind of economically useful properties.

I'd say, ignore this "information," as it has no relevance in our area of interest.
H. difformis, Water Wisteria, is a very aquarium popular plant. Any problematic qualities would be well known by now in our community.
We wouldn't have to read pharmaceutical research papers to discover them.

Or, to put it more simply, "Chill, dude."
 
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Plant tormentor

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Hahaha @ "Chill, dude"!

Thanks Chris, you make some very good points, particularly in relation to the author's motivations and interpretation of the material which I hadn't considered. I did note some aberrations in the material I mentioned such as lack of mention of methodology employed, together with citation of previous source. I also found it unusual that there didn't seem to be much corroboration for the statement however I found a few mentions from various government bodies which while pointing to the same material left the question open. One from the USDA, entitled Weed Risk Assessment for Hygrophila difformis and available at:

https://www.aphis.usda.gov/plant_health/plant_pest_info/weeds/downloads/wra/Hygrophila-difformis.pdf

Stated in relation to toxicity to animals, including livestock/range animals and poultry:

"The ethanol extract of H. difformis leaves has been tested on mice and is considered "a safe drug" that increases the sleeping time of mice and works as an analgesic (painkiller) (Pal and Samanta, 2011). "When first submerged in an aquarium or pond [its] glands produce a toxic substances that may be toxic to some fish...damage seems to give off the toxin. Once they have been in the water a while the poison seems to disappear....It is used for...all type of herbivorous animals for their food" (Krishanu, 2012). The edible leaves of H. difformis are used to treat tooth aches (Pandey and Tripathi, 2010) and as an anticoagulant in India. In parts of Asia, the seed masses of Hygrophila species are consumed by humans (van der Pijl, 1982). Due to the conflicting information, we answered unknown."

Other material I reviewed similarly concluded that actual toxicity was considered to be unknown. Those materials in themselves served as motivator for further digging. My initial interest was actually prompted by a reminder from someone as to an unreferenced mention of toxicity to certain animals. That person was only aware of one purported, although unconfirmed, incidence of toxic interaction, which was in itself one more incidence than I was aware of.

I totally agree with your point that where there toxicity the aquarium and aquatic plant community would in all likelihood have known of the issue, it shouldn't be necessary to hunt as far as pharmaceutical research for information. Given the absence of data within this community however it seemed prudent to widen to search field to other possible avenues of data. Even here, much beyond this paper, data is largely lacking, with little to no corroborative evidence that I've being able to find. That being so, and given deficiencies in the seeming source material together with the lack of data in the aquatic community, I feel your suggestion to ignore this 'information' is a prudent and valid one which I will take on board.

Many thanks. ;)



I've never heard anything about Hygrophila toxicity.

I'd caution you on interpreting the information in the pharmacy research paper to mean anything at all in terms of the plant's effect in an aquarium setting. The author, a pharmacy grad student, post-doc, or already degreed researcher, is looking for a way to publish something, anything, as part of their required professional activity. The paper must provide some kind of new information. The author seems to be looking for some kind of economically useful properties.

I'd say, ignore this "information," as it has no relevance in our area of interest.
H. difformis, Water Wisteria, is a very aquarium popular plant. Any problematic qualities would be well known by now in our community.
We wouldn't have to read pharmaceutical research papers to discover them.

Or, to put it more simply, "Chill, dude."